1. Field of the Invention
The present invention relates to an electrophotographic printer, and more particularly, to an electrophotographic printer based on multi-pass printing.
2. Description of the Related Art
In general, electrophotographic printers form an electrostatic latent image by radiating light on a photosensitive medium charged to a predetermined potential, develop the electrostatic latent image using a toner having a predetermined color image to form a toner image, transfer the toner image onto a recording medium, and fuse the toner image on the recording medium, thereby printing a monochromic or a multi-color image.
Electrophotographic printers are typically classified into wet type electrophotographic printers and dry type electrophotographic printers according to a developer used. A wet type electrophotographic printer uses a developer having powdered toner dispersed in a liquid carrier. A dry type electrophotographic printer uses a two-component developer having a powdered carrier mixed with a toner, or a one-component developer without the carrier. The dry type electrophotographic printer will now be described, and the term “developer” used throughout the specification indicates a toner for convenience sake.
Printing of a color image generally requires yellow (Y), magenta (M), cyan (C) and black (K) toners. Accordingly, four development units for developing the respective color toners are needed. Either a single-pass printing, which requires four exposure units and a photosensitive medium, or a multi-pass printing, which requires a single exposure unit and a photosensitive medium, may be employed in printing a color image. In either case, four development units are necessary.
A single-pass printing process allows high-speed printing for both a monochromic image and a color image because printing is performed in a single pass in both cases. On the other hand, although a multi-pass printing process requires a printing time for a color image four or more times longer than that for a monochromic image, it can be implemented by a simplified structure.